The correct answer is B. The SATA HDD power cable is disconnected, because RAM upgrades require opening the case, which can easily result in accidentally loosening or disconnecting internal cables. If the system cannot detect the boot drive, it will display a “No boot device found” error.
According to the Quentin Docter – CompTIA A+ Complete Study Guide, one of the first troubleshooting steps after hardware changes is to verify that all internal cables—especially SATA data and power cables—are securely connected. A disconnected drive will not be detected by the BIOS or UEFI firmware.
The Travis Everett & Andrew Hutz – All-in-One Exam Guide explains that boot order changes are less likely unless the technician explicitly modified BIOS settings. Similarly, reformatting a drive would not occur during a RAM upgrade.
The Mike Meyers / Mark Soper Lab Manual reinforces that physical connection issues are among the most common causes of boot failures following hardware maintenance. A disconnected power cable prevents the hard drive from spinning up, making it invisible to the system.
Because the issue appeared immediately after opening the case for a RAM upgrade, the most likely cause is a disconnected SATA power cable, making B the correct answer.
